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Thread: how does a Garmin work out mph

  1. #1
    Senior Member SEFTON's Avatar
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    how does a Garmin work out mph

    How accurate are the mph on a Garmin.

    Lets say I ride for 1 hour with a number of hills & one stop for 10mins. My average mph is 13mph.

    Does the Garmin simply do an average on the lowest & highest speed?

    Or

    Does the Garmin calculate how much time is spent at every speed and then do an average?

    Also what’s a decent mph on a road bike but riding loads of hills (west Lancashire – Haslington, Accrington, Rossendale, Rivington, Belmont, Edenfield etc)

  2. #2
    Master nikalas's Avatar
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    Re: how does a Garmin work out

    If you've cover X miles in a certain time then an average speed calculated by dividing distance by time is 100% accurate regardless of how often the speed is sampled.

    If you don't want your stop factored in, just set your Garmin to only record moving time or stop it when you stop.

    Hard to say what's a decent mph.. too many factors to consider and how long you're riding for.

  3. #3
    Master ba-ba's Avatar
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    Re: how does a Garmin work out

    when you upload you'll be given 'average speed' (i.e. average speeds of the distance the watch has measured when you turned it on) and 'average moving speed' (basically the average speed of your 'moving' time)
    Quite how Garmins measure 'moving' time/how the autopause function works I'm not too sure, as I've had a few times it's reckoned I've stopped moving for about 1mi+n on a race, when I definitely haven't! This may be due to stiles/gates (I don't normally have to wait at these) or, if you're slogging up a particularly arduous hill, your horizontal movement is so limited the Garmin reckons you've stopped!
    Either way I tend to ignore 'moving' time.
    Nic Barber, Pennine. Downhill Dandy

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    Master Penguin's Avatar
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    Re: how does a Garmin work out

    how can i get the garmin to understand i'm trying to run up a hill, notice on download it takes it in as the crow flies rather than include the climbing distance with the mileage? hope that makes sense, otherwise learn penguense
    penguins happy feet :w00t:

  5. #5
    Member charlieB's Avatar
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    Re: how does a Garmin work out

    I once worked out 'climbing distance' by trigonometry after a long steepish run in the lakes and found it to be neglible. It did not really give me any extra useful information compared to basic length and ascent statistics so I never bothered doing it again.

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    Senior Member superflyguy's Avatar
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    Re: how does a Garmin work out

    Quote Originally Posted by Penguin View Post
    how can i get the garmin to understand i'm trying to run up a hill, notice on download it takes it in as the crow flies rather than include the climbing distance with the mileage? hope that makes sense, otherwise learn penguense
    as far as I know (and I didn't design the software) a garmin can't work this out and as CharlieB alludes "what's the point". All race/challenge distances are measured as the crow flies. I suspose there may be some value in working out as an academic exercise, but real life application is pretty limited : unless of course you are looking for a couple of extra miles for your yearly total!
    Adam Speed
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    Master Penguin's Avatar
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    Re: how does a Garmin work out

    Quote Originally Posted by superflyguy View Post
    as far as I know (and I didn't design the software) a garmin can't work this out and as CharlieB alludes "what's the point". All race/challenge distances are measured as the crow flies. I suspose there may be some value in working out as an academic exercise, but real life application is pretty limited : unless of course you are looking for a couple of extra miles for your yearly total!
    no just given myself reason for running up big hills at a penguin pace, it shows some kind of penguin effort.. be it slow!
    penguins happy feet :w00t:

  8. #8
    Master L.F.F.'s Avatar
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    Re: how does a Garmin work out

    Move somewhere with no big hills. Makes life much simpler.

  9. #9
    Master XRunner's Avatar
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    Re: how does a Garmin work out

    Quote Originally Posted by Penguin View Post
    how can i get the garmin to understand i'm trying to run up a hill,
    I tend to rely on my senses detecting that my front foot is coming to rest at a higher elevation than the back foot.

    Why on earth would anybody want a machine to tell them that they are running up a hill?
    Fox Avatar "Protected" by Hester Cox - Printmaker

  10. #10
    Master Stolly's Avatar
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    Re: how does a Garmin work out

    Quote Originally Posted by Penguin View Post
    how can i get the garmin to understand i'm trying to run up a hill, notice on download it takes it in as the crow flies rather than include the climbing distance with the mileage? hope that makes sense, otherwise learn penguense
    Climbing distance though amounts to pretty much bugger all. Take the 3 peaks for example which for simplicity assume to be 23.5 miles long with roughly 1 mile of aggregate climb. Now draw a line 23.5 inches long and draw a one inch high line in the middle of it and complete the triangle. I think you will find that the total length of the line taking into account the total ascent, the top two lines of a very flat and extended triangle, is 23.5 inches and a teeny weeny little bit

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